Dr. Prabhjot Singh, an observant Sikh who wears a turban and has a beard, was walking on the street in upper Manhattan on Saturday night when he was attacked by a group of young men on bikes who surrounded him. The suspects shouted anti-Muslim statements, knocked the professor down and beat him.

According to Dr. Singh, the assailants called him "Osama" and "terrorist" as they punched him in the head repeatedly. He suffered a fractured jaw and bruising and swelling across his face.

Last night, I received the kind of phone call that everyone dreads: a close friend was hurt, and on his way to the hospital. But the news got worse, as I learned that my friend, Dr. Prabhjot Singh, a young Sikh American professor at Columbia University, had been brutally attacked on a public street, the victim of a violent hate crime. My brother and I immediately jumped in a taxi and rushed to the hospital, where we finally saw Prabhjot being wheeled in, bloody and bruised, his face swollen from a fractured jaw. He couldn't speak because many of his teeth had been displaced, but he waved limply to let us know that he was okay.

We joined Prabhjot in his hospital room and were surprised to find it already filled with officers from the NYPD and its Hate Crime Task Force. As he struggled to give his statement, we came to learn that his assailants had taunted him as they beat him, calling him "Osama" and "terrorist." He described being punched in the face repeatedly until falling to the ground. And then he recalled how the punches to the head continued as he laid on the sidewalk.

Dr. Singh, an assistant professor in the School of International and Public Affairs, co-wrote a New York Times op-ed with Simran Jeet Singh last year on the importance of gathering more information on hate crimes against Sikhs. Sadly, it's a lesson that became all too real, and reinforced firsthand.